Employee Pension Plans (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Summary of net periodic benefit cost
Interest cost	$ 975	$ 1,053	$ 1,950	$ 2,106
Expected return on plan assets	(1,088)	(1,203)	(2,176)	(2,406)
Amortization (adjustment) of net loss	456	427	912	854
Other	213	150	426	300
Net periodic benefit cost	$ 556	$ 427	1,112	854
Company contribution			1,400	$ 800
Expected contributions remainder of current fiscal year			$ 1,200